This patent disclosure concerns apparatus for performing the required liquid propane discharge on cloud seeding rockets and the inclusion of special additives to the liquid propane in order to increase the efficiency of its ice nucleation.
The seeding of a supercooled cloud for purposes of weather modification requires introduction of ice crystal seeds into it in a large defined amount at an appropriate time and position of the cloud. Conventional seeding agents, such as silver iodide and dry ice, have a number of shortcomings in their practical applications. Problems with silver iodide include the high cost, the low ice crystal production at low altitudes combined with the undersirably large numbers at high altitudes, the downwind effect due to seeding agent survival, the slow ice nucleation rates at warm temperatures, and the possible adverse ecological effect due to the toxicity of the slver ions.
The use of dry ice also has its own problems, such as the difficulty of long term storage and the need for dry ice pellet preparation. Moreover, costly, high-flying aircraft are required for dispensing pellets from a position above the cloud. Conventional rocket seeding devices cannot be used, since the dry ice pellets have no self-contained power means for discharging them from the rockets, apart from the difficulty of its long term storage.
Liquid propane (LP) is known to generate large numbers of ice crystals in supercooled clouds due to extremely low temperatures induced by its evaporative cooling. The number of ice crystals per gram of liquid propane is comparable to that of one gram of dry ice. In addition to its high efficiency for ice nucleation, liquid propane has a number of practical advantages over both silver iodide and dry ice, particularly when rapid generation and spreading of a large number of ice crystals are required, such as seeding of vigorously growing convective clouds for hail-suppression purpose. The main advantages of liquid propane nucleant are that it is inexpensive, non-toxic, ecologically safe and available almost anywhere due to easiness for its long term storage, coupled with its instantaneous ice nucleation. There is no possibility for any downwind effect of ice crystal nuclei survival because the ice crystals evaporate or melt in dry or warm environments during the drift toward downwind areas. In addition, the high vapor pressure of liquid propane can be conveniently utilized for its automatic and rapid discharge from a flying rocket. In this regard, the liquid propane utilized on fast rockets is highly advantageous for cloud seeding applications where immediate seeding and ice crystal generation are required, such as in hail suppression operations.
It is an objective of this invention to provive improved apparatus for discharging liquid propane in a cloud-seeding rocket.
It is a further objective to provide for the admixing of additives to liquid propane to enhance the production of ice crystals by the liquid propane.